1. Field of the Invention
The field of the invention relates to the control of aquatic weeds in canals, rivers, ponds, lakes and impoundments.
2. Description of the Prior Art
The problems of controlling the growth of organisms in aqueous systems are serious and growing in severity. Submerged aquatic weeds, for example, cause major problems in water distribution and irrigation systems. The growth of weeds in irrigation canals greatly reduces the conductivity and capacity of such systems with resulting substantial economic loss. Large sums are therefore being spent in the mechanical and other methods of removal of weed growths from irrigation canals, especially in the southern and western parts of the United States.
Because of the great difficulties involved in the mechanical removal of weeds and other undesired forms of aquatic life from irrigation canals, ponds, lakes, impoundments, etc., it has been proposed to utilize chemical control. Accordingly, various types of chemicals have been added to such bodies of water.
In the prior art, Offenlegungsschrift No. 2,017,842 (Nov. 5, 1970), teaches the use of some thiadiazoleureas substituted in the 5-position of the thiadiazole ring with alkenylthio, alkynylthio, and other substituted thio substituents. The compounds are alleged to be terrestrial growth regulators and herbicides. There is no teaching that the compounds are useful against aquatic weeds and none of the tests described in the document suggest the compounds would be active as aquatic herbicides. In addition, the compounds are structurally different from those included within the scope of the instant application.
Also in the prior art is Dutch Patent No. 69,06983 (Nov. 25, 1969), which teaches 1,3,4-thiadiazolylureas having, inter alia, a trifluoromethyl group in the 5-position of the thiadiazole ring and an aryl or substituted aryl group attached to the urea nitrogen farthest removed from the thiadiazole ring. These Dutch compounds are taught as being useful as either total or selective terrestrial herbicides when applied pre- or postemergent against weeds in cotton and grain crops. The compounds also are taught as being active against snails, phytopathogenic fungi, insects and mites. However, there is no teaching that the compounds would be active as aquatic herbicides.
In addition, British Patent No. 1,250,624 (Oct. 20, 1971), teaches a series of compounds useful in biocidal preparations, one of which compounds is identified as 1-(1,3,4-thiadiazol-2-yl)-3-(.alpha.,.alpha.,.alpha.-trifluoro-p-tolyl)ure a. The biocidal preparations are alleged to act as general microbiocides useful to protect timber, wool, paper, textiles, plastics, hides, synthetic fibers, rubber, dyestuffs, or dyepastes, building materials, adhesives, oils, waxes, cork, cosmetics and detergents against damage by bacteria and fungi. The compounds are also alleged to act as ingested agents in plant protection, as agents against tapeworms, liver flukes, nematodes and anopheles (larvae), against the various excitants of coccidiosis, as timber protection agents in storage protection, as anticaries agents, as chemical sterilizing agents, and against mollusks, lampreys, tube-dwelling worms, mussels, algae, hydroids, water snails and land snails, termites, ticks, amoeba, schistosomes, salmonellae, trichomonads, filaria, protozoa, plasmodia, trematodes, trypanosomes, viruses and the like. However, there is no teaching that the compounds would be active against or useful in the control of aquatic weeds.
The search for an effective aquatic herbicide continues, since there exists a very distinct need for a method of controlling the growth of aquatic weeds.